Pregnancy and lactation place great demands on the maternal organism; under normal circumstances a healthy, fully mature woman of normal weight enters pregnancy, gains an amount adequate for fetal needs and the extra tissues and fluids laid down in her own body and stores some extra weight, almost exclusively fat, in preparation for lactation. With lactation the body is depleted of the additional stores and then there follows a recovery period when the body returns to essentially the prepregnant state. All too often, however, this normal pattern is disturbed. The woman may be underweight or overweight before pregnancy, weight gain during pregnancy may be inadequate or excessive; lactation may be prevented or stopped early; a second pregnancy may follow all too soon. Little is known of the effects of the normal reproductive cycle (pregnancy, lactation & recovery) on maternal fat stores or lean carcass. Even less is known of the effects of a disturbed reproductive cycle. Maternal obesity or excessive depletion which might affect future lactational or gestational performance are just two possibilities. This research proposal will attempt to compare the effects of normal and disturbed cycles on maternal total fat stores and lean carcass and on adipocyte size and number of selected fat depots. Circumstances where either lactation or the recovery is prevented, where early overnutrition or undernutrition permanently alters maternal prepregnant stores and where late overnutrition or undernutrition alters maternal stores just prior to and during pregnancy will be investigated. Food intake will also be monitored and related to the other findings. The findings will increase understanding of the consequences of normal pregnancy, lactation and recovery on underlying obesity or underweight which may have important clinical implications in developing guidelines for advice regarding breast feeding and subsequent recovery intervals which will be optimal for the mother, the present infant, and planned future infants.